-What is enamelware
-What is graniteware
-What is agateware
-Making porcelain enamel
-Enamelware and high heat
-Coating & metal thickness
-How to clean enamelware
-Enamelware and corrosion
-Enamelware as heat conductor
-Enamelware is recyclable
What is enamelware?
Enamelware is made with a base metal of steel, iron or aluminum that is
covered with a glass-like material called porcelain enamel. It is also
referred to as porcelain on steel, cast iron enamel, vitreous enamel,
agateware, and graniteware. The process is thousands of years old, found in
many cultures and of unknown origin. Mass production of enameled kitchen
utensils started in the latter part of the 19th century in the Americas.
What is graniteware?
Graniteware is a type of enamel, and is so named because its composition also includes granite, from which it gets its particular coloration. This process was started and patented by the Niedringhaus brothers in 1874, in the city now known as Granite City, Illinois.
What is Agateware?
Agateware is indicative of the design, generally with variegated curved and colored bands and other markings.
Making Porcelain Enamel
The process of making porcelain enamel begins with clays, electrolytes, metal oxides and water, just as in making glass. The mixture includes materials such as borax, feldspar, quartz and titanium dioxide, which are liquefied at very high temperatures. Poured from a smelter, the mixture is quenched between water-cooled rollers to form a quick-cooled ribbon of glass, which is then shattered to form a particulate known as frit. Frit is applied to metal using either a wet dipping or spraying, or a dry method, generally in multiple coatings, then fired at very high temperatures (932-1652° F). While in the furnace, the frit melts, bonding with the metal to create an inseparable compound, resulting in a new, chemically unique finish.
The final coatings of frit usually include color and determine appearance (smooth, pebbly, stippled, matte or glossy). Pigments, primarily inorganic compounds fused into the glass matrix, are extremely stable during aging. While glossy, acid resistant porcelain enamels are not photosensitive, matte-finish and some types of highly pigmented red and yellow porcelain enamels may show some fading after several years of weathering, and alkali resistant porcelain enamels are not necessarily acid resistant.
Enamelware and High Heat
Enamel can usually be safely subjected to high heat, and can generally take abrupt temperature changes of 200-300° F without damage. Although very hard, a thin coating (1-mil or less on steel or aluminum) can flex more with the base metal as it expands and contracts with heat and cold. A thick coating (125-mils or more) can be effectively used over iron and heavy gauge steel, as its rate of expansion and contraction is much less than that of thinner metals.
Coating and Metal Thickness
The thickness of both the metal and the coatings is one of the most important determining factors in the longevity of porcelain enamel. Generally, a thinner coating will have greater flexibility and a lesser likelihood of fracturing. Porcelain enamel becomes as hard as the base metal, and will not break unless the base metal fractures or becomes deformed. Its hardness is generally measured from 3.5-6 Mohs (organic finishes in the 2-3 range), and its compressive strength is in the range of 20,000 psi.
Enamel is usually quite even and smooth, very resistant to abrasion, does not rust or burn, and retains its original gloss and color. It is completely resistant to attack by common organic solvents, dyes, greases and oils, it is non-porous, impervious to bacteria and most chemicals, and very easy to clean. Its dense surface makes it the second most stick-resistant material, next to fluoropolymers.
How to Clean Enamelware
Most cleaning can be performed using only water and a mild detergent. Boiling water in the pan and letting it soak can usually loosen sticking food, which can then be removed with a nylon scourer or wooden scraper. The build-up of lime and calcium deposits from water may be removed by boiling a solution of vinegar and water.
Boiling water with baking soda (2 tsp per quart) can be effective for tough tasks. Cleaning stubborn sticking and stains can also be accomplished by using 1 tbsp trisodium phosphate to 1 quart of hot water, or soak 2-3 hours with a solution of 1 tsp of bleach per pint of water. Acetic and muriatic acids are effective in removing certain stains, but they will also remove part of the surface coating of the porcelain.
If you must use scouring powder it should be of the very finest grit, such as Bon Ami or Bar Keeper's Friend. For heavy baked-on grease, or spills, you can occasionally use a fine steel wool pad or scrape with a razor blade, however do not scratch the enamel, or it will be harder to clean afterwards. If you use chlorine or hydrogen peroxide bleach, do not use these full strength or let them remain on the surface for more than a few seconds. Rinse the surface thoroughly.
Enamelware and Corrosion
Enamel can corrode through repeated or prolonged contact with acidic elements. Boiling water slowly damages enamels over a long period of time, and soft water will corrode enamels faster than hard water. Enamel will easily withstand repeated freezing and thawing of liquids, however over time this will cause some lesser quality enamels to chip or splinter.
Special paints are available to repair enamel, however these should not be used on cooking utensils.
The enamel finish on many appliances (refrigerators, the sides of stoves, and other appliances that are not subjected to high heat) is usually synthetic, or may be applied by an electrostatic process called powder coating. Although very hard, its thinness does not have the same scratch-resistant properties as regular baked-on enamel.
Enamelware as a Heat Conductor
Enamel is a relatively good heat conductor when applied in thin coats, however it is not a thermal insulator or diffuser. Avoid over-heating and pre-heating empty, and use a heat diffuser under enameled pans made of thin steel and aluminum.
Enamelware is recyclable
Enamel does not hinder the recyclable nature of the material that it covers.